Catalyst for the production of hydrocarbons and process for their production

ABSTRACT

A catalyst for the production of hydrocarbon consists essentially of crystalline aluminum silicate, at least one compound of the metal zinc and/or cadmium and additionally silica. The catalyst is produced by heating a crystalline aluminum silicate, in a given case partially or completely converted to the hydrogen form, with a zinc and/or cadmium compound and molding with a silica containing binder.

BACKGROUND OF THE INVENTION

The invention is directed to a catalyst for the production ofhydrocarbons having a higher ethane selectivity from synthesis gas (amixture of carbon monoxide and hydrogen).

An important chemical raw material for the chemical industry isethylene, which is produced to a great extent by cracking petroleumderivatives. In view of the expense and scarcity of petroleum products,it is also known to convert synthesis gas to a hydrocarbon mixturehaving the highest possible content of ethane, which then is furtherprocessed to ethylene (see Chang U.S. Pat. No. 4,096,163. The entiredisclosure of Chang is hereby incorporated by reference and relied uponincluding the U.S. patents mentioned therein).

The industrially desired product is ethylene. This is obtained fromparaffin hydrocarbons having at least two carbon atoms by cracking,whereby the highest yield is obtained from ethane. For this reason, itis desired to carry out the transfer of synthesis gas into hydrocarbonsin such manner that there is obtained the highest possible content ofethane in the product gas mixture. In view of the very large amountswhich are reacted in industrial plants, a slight improvement of theselectivity or the space-time-yields already represents a significantindustrial advance.

It is known to reduce aliphatic hydrocarbon from synthesis gas (seeChang U.S. Pat. No. 4,096,163, col. 13, example 7). The catalystemployed thereby is a zinc exchanged ZSM-5/aluminum oxide-extrudate. Thehydrocarbon gas mixture obtained in addition to methane, isobutane, andisopentane (36.4% ethane and 11.9% propane).

Since the yield of ethane of the known process does not have the desiredselectivity, there is a need to develop a corresponding catalyst.

SUMMARY OF THE INVENTION

The object of the invention is a catalyst for the production ofhydrocarbons having higher ethane selectivity consisting of (orconsisting essentially of) crystalline aluminum silicate at least onecompound of the metals zinc and/or cadmium and also silica.

Of especial interest as crystalline aluminum silicate is a zeolite. Thezeolite can be of the structure type faujasite, mordenite and/orPentasil (e.g., ZSM-5 and ZSM-11). Pentasil is described by Doelle et alin Journal of Catalysis, Vo. 71, pages 27-40 (1981). The entiredisclosure of the Doelle article is hereby incorporated by reference andrelied upon.

In a further illustrative form of the invention, the zeolite can beemployed in pretreated form. A preparation of this type for example canbe an ion exchange, an impregnation, or a mixture with anothercomponent, preferably a compound of the metal, zinc and/or cadmium.

As metal, there is preferably present zinc. The supplementary silica canbe present in the catalyst of the invention in amounts of 5 to 30 weight%, preferably 10 to 20 weight %, particularly 15 weight %, based on thealuminum silicate in powder form employed.

The zinc (and/or cadmium) content (calculated as ZnO or CdO) of thecatalyst can be 0.1 to 30 weight %, preferably 0.5 to 3 weight %.

In a specific illustrative form, the zeolite used as aluminum silicatecan have the following x-ray diffraction diagram with the followingcharacteristic interferences:

    ______________________________________                                               d-value    Int.                                                        ______________________________________                                                11.17 ±  0.1                                                                         52                                                                  10.05 ±  0.1                                                                         35                                                                  6.34 ± 0.1                                                                            5                                                                  4.98 ± 0.03                                                                           4                                                                  4.35 ± 0.03                                                                          18                                                                  4.27 ± 0.03                                                                          23                                                                  3.85 ± 0.03                                                                          100                                                                 3.74 ± 0.03                                                                          54                                                                  3.66 ± 0.03                                                                          22                                                                  3.34 ± 0.03                                                                           8                                                                  2.98 ± 0.02                                                                          12                                                                  2.49 ± 0.02                                                                          12                                                                  2.00 ± 0.02                                                                           8                                                          ______________________________________                                    

This type of zeolite which is of the type Pentasil can be produced byreaction of a mixture of water, sodium aluminate, sodium hydroxide,precipitated silica, and ##STR1## at a temperature of 50° to 200° C.under autogenous pressure in an autoclave and subsequent conversion intothe hydrogen form.

The conversion into the hydrogen form can be carried by a knowntreatment with acids, preferably with mineral acids such as, e.g.,sulfuric acid, hydrochloric acid, or nitric acid.

Likewise, the conversion into the hydrocarbon can be carried out byexchange with ammonium ions and subsequent calcination.

The conversion into the hydrogen form can be carried out completely orpartially. In a preferred illustrative form, the Na₂ O content of thecrystalline aluminum silicate converted into the hydrogen form can beless than 0.1 weight %.

The template compound ##STR2## used can be produced as follows:

Tetradecene oxide (1) is reacted in known manner with methyl mercaptanto the sulfide (2) and this product is reacted with methyl iodide toform the end product (3). ##STR3##

In a particular illustrative form, the catalyst of the invention can bepresent in shaped form, e.g., granulated, pelletized, extruded ortabletted.

In this form, the catalyst, if the pretreatment is carried out with azinc compound, can have the following composition:

0.002 to 0.5 Wt.-% Na₂ O

0.1 to 30 Wt.-% ZnO

0.4 to 5 Wt.-% Al₂ O₃

60 to 98 Wt.-% SiO₂

2 to 15 Wt.-% Loss on calcining (DIN 51081)

For example, the composition can read as follows:

0.01 Wt.-% Na₂ O

0.66 Wt.-% ZnO

1.39 Wt.-% Al₂ O₃

91.51 Wt.-% SiO₂

5.4 Wt.-% Loss on calcining (DIN 51081)

Furthermore, the catalyst of the invention in shaped condition can havethe following physical-chemical properties:

(a) BET-Surface area 539 m² /g

(b) Hg-Compressed volume 0.99 cm³ /g

(c) Sorption of n-Hexane 0.12 g/g, Benzene 0.06 g/g, 3-Methylpentane0.09 g/g and water 0.06 g/g at p/_(po) =0.5 and T=23"c

A further object of the invention is the process for production of thecatalyst for the production of hydrocarbons with higher selectivity forethane which are characterized by treating a crystalline aluminumsilicate, preferably of the Pentasil type, in a given case eitherpartially or completely converted into the hydrogen form, with a metalcompound and molding with a silicon dioxide binder.

The treatment of the crystalline aluminum silicate, preferably Pentasil,with a metal compound can be carried out through ion exchange with ametal salt solution, impregnation with a metal salt solution, or mixingwith solid metal oxide.

As metal compounds, there can be employed the oxides and/or the salts,as e.g., chloride, sulfate, nitrate, acetate, and others of zinc and/orcadmium.

The ion exchange can be carried out with an excess of zinc ions inaqueous solution in known manner. Thereby, there can be started withboth the sodium form and also the hydrogen form of the crystallinealuminum silicate.

Since the sodium content of the catalyst preferably should be a low aspossible, the impregnation (which term includes a drying) is carried outwith aqueous zinc salt solution or the mixing with metal oxidepreferably with a crystalline aluminum silicate of structural typePentasil in the hydrogen form.

The amounts of metal compound added thereby corresponds to the finestmetal content of the crystalline aluminum silicate.

As silica containing binder, there can be employed in a preferredillustrative form silica sol or silica gel.

The molding of the crystalline aluminum silicate can take placeaccording to known procedures.

For example, the molding can be carried out by addition of silica sol(40% silicon dioxide) to the aluminum silicate powder until reaching amoldable consistency and with subsequent shaping on a granulation plate.Likewise, a granulation is possible through, e.g., extrusion.

The catalyst of the invention can be employed for the production ofhydrocarbons having higher ethane selectivity from synthesis gas(hydrogen and carbon monoxide).

As the gas employed, there are suited synthesis gas having varyingamounts of hydrogen and carbon monoxide, as is known from the state ofthe art concerning the conversion of synthesis gas to hydrocarbonshaving a high ethane content. The synthesis gas without disadvantage canalso contain smaller amounts of other gases such as carbon dioxide,methane, other lower hydrocarbons, e.g., propane, nitrogen, and gaseoussulfur compounds.

The molar ratio of hydrogen to carbon monoxide, suitably is in the rangeof 0.5:1 to 4:1, preferably in the range of 1:1 to 2:1. The possibilityof using synthesis gas having this type of hydrocarbon is a specialadvantage of the catalysts of the invention since the synthesis gas canpractically pass into the composition resulting from the carbongasification without enrichment with hydrogen and without expensive gaspurification.

The pressure used lies in the ranges that are known in the art, wherebyin the selection of the operating pressure besides the purelyreaction-kinetics factors there can also be considered the pressure ofthe synthesis gas available and/or the pressure desired for the productgas. As especially suited, there has proven a total-reaction pressure of5 to 400 bar, preferably of 20 to 200 bar, and especially preferredbelow 150 bar.

The reaction temperature likewise can be varied within wide limits as inaccordance with the state of the art, whereby a range of 300° to 550°C., and especially of 340° to 460° C. is preferred. It is an advantageof the process according to the invention that the conversion can becarried out at relatively high temperatures with excellent results.

The process according to the invention can be carried out with solid bedor fluidized bed catalyst. There can be employed the same reactors asare used according to the state of the art for conversion of synthesisgas. Examples of suitable reactors are those which are also employed forthe methanol-synthesis, e.g., step reactors having cold gas addition,step reactors having intermediate cooling, tube reactors having internalor external cooling. The removal of heat is carried out according to thestate of the art, e.g., by liquids or gases.

There can also be employed reactors such as are known for theFischer-Tropsch synthesis; e.g., tube reactors, step reactors, fluidizedbed reactors, or

According to the process of the invention, a hydrocarbon mixture havinga very high portion of ethane is obtained at good space-time-yields.Besides ethane, as is according to the state of the art, there areformed substantially methane, ethylene, propane, propylene, andisobutane.

The gas mixture obtained according to the invention can be used invarious ways, e.g., by mixing with natural gas to increase the heatingvalue. A specially important use industrially, however, is in theproduction of ethylene. For this purpose, the ethane and the higherhydrocarbons are separated according to known process from thehydrocarbon-gas mixture obtained, e.g., by pressure washing with mineraloils. The separated ethane and the higher hydrocarbons are convertedinto ethylene according to known processes in the art. (See Ullmann'sEnzyklopadie. Tech. Chem. 4th Edition, Vol. 8, pages 158-194). Theentire disclosure of Ullmann is hereby incorporated by reference andrelied upon.

The catalyst can consist of or consist essentially of the statedmaterials; and the process can comprise, consist essentially of, orconsist of the stated steps with the recited materials.

DETAILED DESCRIPTION EXAMPLES

A. Production of the Catalyst

EXAMPLE 1

5 grams of sodium aluminate and 25 grams of NaOH were dissolved in 50 mlof H₂ O and added to a suspension of 200 grams of precipitated silicaand 75 grams of C₁₂ H₂₅ CHOHCH₂ --S.sup.⊕ (CH₃)₂ I.sup.⊖ in 2000 ml ofH₂ O. The mixture was stirred for 80 hours at 160° C. in an autoclaveunder autogenous pressure, filtered off and washed to pH 9 with H₂ O.The wet filter cake was suspended in 2 liters of ethyl alcohol, filteredoff, washed with ethyl alcohol, and dried at 120° C. 100 grams of thedried silicate were stirred in 1 liter of 2 normal HCl for 2 hours at80° C., filtered off, washed with water until neutral, and dried at 120°C.

Analysis: 0.06% Na₂ O, 1.74% Al₂ O₃, 91.1% SiO₂, 3.2% Loss on Calcining.

The aluminum silicate had an x-ray diffraction diagram (pattern) havingthe following characteristic interferences:

    ______________________________________                                               d-Value    Int.                                                        ______________________________________                                               11.17 ± 52.1                                                               10.05 ± 35.1                                                               6.34 ± 0.1                                                                             5                                                                 4.98 ± 0.03                                                                            4                                                                 4.35 ± 0.03                                                                           18                                                                 4.27 ± 0.03                                                                           23                                                                 3.85 ± 0.03                                                                           100                                                                3.74 ± 0.03                                                                           54                                                                 3.66 ± 0.03                                                                           22                                                                 3.45 ± 0.03                                                                            7                                                                 3.34 ± 0.02                                                                            8                                                                 2.98 ± 0.02                                                                           12                                                                 2.49 ± 0.02                                                                           12                                                                 2.00 ± 0.02                                                                            8                                                          ______________________________________                                    

EXAMPLE 2

50 grams of aluminum silicate according to Example 1 were stirred in asolution of 136.3 grams of ZnCl₂ in 500 ml of H₂ O for one hour at 80°C., filtered off, washed with water, and dried. The zinc treatedaluminum silicate obtained had the following composition:

0.01 Wt.-% Na₂ O

1.63 Wt.-% Al₂ O₃

92.5 Wt.-% SiO₂

0.74 Wt.-% ZnO

EXAMPLE 3

50 grams of aluminum silicate according to Example 1 without acidtreatment (0.75% Na₂ O. 1.52% Al₂ O₃. 89.6% SiO₂) were stirred into asolution of 500 grams of ZnCl₂ in 500 ml of water for two hours at 80°C. and subsequently worked up as described in Example 2.

The zinc treated aluminium silicate obtained had the followingcomposition:

0.18 Wt.-% Na₂ O

1.15 Wt.-% Al₂ O₃

85.9 Wt.-% SiO₂

1.17 Wt.-% ZnO

EXAMPLE 4

50 grams of aluminum silicate as described in Example 1 were suspendedin a solution of 1.25 grams of ZnCl₂ in 100 ml of water and stirred for2 hours at 80° C. The mixture obtained was dried at 50° C./50 mbar.

The zinc treated aluminum silicate obtained had the followingcomposition:

0.03 Wt.-% Na₂ O

1.54 Wt.-% Al₂ O₃

89.7 Wt.-% SiO₂

1.5 Wt.-% ZnO

EXAMPLE 5

50 grams of aluminum silicate according to Example 1 in the hydrogenform and 1.5 grams of ZnO were suspended in 100 ml of water and stirredfor 2 hours at 80° C. The mixture obtained was dried at 50° C. and apressure of 50 mbar.

The zinc salt pretreated silicate obtained had the followingcomposition:

0.04 Wt.-% Na₂ O

1.70 Wt.-% Al₂ O₃

89.6 Wt.-% SiO₂

2.9 Wt.-% ZnO

EXAMPLE 6

The aluminum silicate employed as in Example 4 was treated analogouslywith an aqueous zinc acetate solution. Under otherwise identicalconditions, there were used 4.3 grams of zinc acetate. The zinc saltpretreated aluminum silicate obtained was subsequently calcined at 440°C. and had the following composition:

0.02 Wt.-% Na₂ O

1.26 Wt.-% Al₂ O₃

88.5 Wt.-% SiO₂

3.1 Wt.-% ZnO

EXAMPLE 7 Shaping

50 grams of pretreated powdery aluminum silicate according to Examples 1to 6 were mixed with 15 ml of 40% silica sol and 15 ml of water to forma pasty composition and shaped in the granulating plate. After thedrying (4 hours at 120° C.), the granulates were calcined at 440° C. andsieved. The fraction 0.5 to 1 mm was used for the reaction of thesynthesis gas.

B. Reaction of CO/H₂

EXAMPLE 1

A synthesis gas mixture, which contains H₂ and CO in the molar ratio2:1, was led over the catalyst bed at a temperature of 400° C., apressure of 80 bar and a volume related space velocity of 500 h⁻¹.

The results obtained thereby are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                        Conversion of Synthesis Gas On Aluminum Silicate                              According To Example A 2 Which Was Shaped                                     According to Example 7                                                        ______________________________________                                        Temperature ° C. 400                                                   Pressure, bar            80                                                   Space Velocity                                                                Volume/Volume h         500                                                   Conversion of CO to      18                                                   Hydrocarbons %                                                                H.sub.2 /CO in           2                                                    Total Conversion of      25                                                   Synthesis Gas %                                                               Distribution of Hydrocarbon Wt. %                                             Methane                  22                                                   Ethane                   70                                                   Propane                  5                                                    C.sub.4.sup.+            3                                                    ______________________________________                                    

EXAMPLE 2

The conversion of the synthesis gas was carried out in a fixed bedreactor having a diameter of 10 mm and 60 ml of reaction space. Therewere filled into the reactor 40 ml of the catalyst obtained according toproduction Example A 2. The catalyst was activated by leading nitrogenthrough it in an amount of 10 l/h at 450° C. under a pressure of 2 barsfor 4 hours.

The synthesis gas was led through the reactor whereby composition, spacevelocity, reaction temperature, and reaction pressure are collected infollowing Table 2. In this table, there are given the total conversionof synthesis gas, the conversion of carbon monoxide to hydrocarbons andthe distribution of the hydrocarbons.

The gas mixture leaving the reactor was relieved of pressure and ledthrough a cooling trap at -20° C. No condensation product was depositedin the cooling trap. The gas mixture leaving the cooling trap was ledthrough gas sample tubes for analysis.

                  TABLE 2                                                         ______________________________________                                        Synthesis gas, H.sub.2 :CO                                                                     1.65    1.65    1.65  1.65                                   Space Velocity   500     500     500   500                                    Volume/Volume · h                                                    Reaction Temperature, °C.                                                               350     350     350   350                                    Reaction Pressure, bar                                                                         80      200     300   400                                    Total Conversion of                                                                            4       6       10    12                                     Synthesis Gas                                                                 Conversion of CO to                                                                            4       7       9     11                                     Hydrocarbons, %                                                               Distribution of Hydrocarbons                                                  Wt. %                                                                         Methane          18.5    24.0    24.0  25.1                                   Ethane           50.0    42.1    37.0  30.6                                   Propane          4.5     8.0     9.9   10.2                                   Butane and Higher                                                                              27.0    25.9    29.0  34.0                                   ______________________________________                                    

EXAMPLE 3

The procedure was as described in Example B 2, whereby the processparameters and results are collected in the following Table 3.

                  TABLE 3                                                         ______________________________________                                        Synthesis gas, H.sub.2 :CO                                                                 1.62    1.62    1.62  1.62  1.62                                 Space Velocity                                                                             500     500     500   500   500                                  Volume/Volume · h                                                    Reaction Tempera-                                                                          350     375     400   425   450                                  ture, °C.                                                              Reaction Pressure, bar                                                                     100     100     100   100   100                                  Total Conversion of                                                                        6.6     8.8     14.5  19.9  22.5                                 Synthesis Gas %                                                               Conversion of CO to                                                                        5.8     6.5     12.5  18.2  20.3                                 Hydrocarbons %                                                                Distribution of Hydro-                                                        carbons Wt. %                                                                 Methane      27.3    29.8    29.6  30.0  50.2                                 Ethane       49.5    56.2    60.6  60.7  39.8                                 Propane      12.1    6.8     6.8   6.8   5.9                                  Butane and Higher                                                                          11.1    7.2     3.1   2.5   4.2                                  ______________________________________                                    

EXAMPLE 4

The procedure was as described in Example B 2, whereby the processparameters and results are collected in the following Table 4.

                  TABLE 4                                                         ______________________________________                                        Synthesis Gas, H.sub.2 :CO                                                                         1.18    1.65    3.0                                      Space Velocity       500     500     500                                      Volume/Volume · h                                                    Reaction Temperature, °C.                                                                   400     400     400                                      Reaction Pressure, bar                                                                             100     100     100                                      Total Conversion of  24.9    14.5    17.9                                     Synthesis Gas, %                                                              Conversion of CO to  20.1    12.5    16.0                                     Hydrocarbons, %                                                               Distribution of Hydrocarbons Wt. %                                            Methane              37.5    29.6    48.0                                     Ethane               45.0    60.6    36.5                                     Propane              10.2    6.8     8.6                                      Butane and Higher    7.3     3.1     6.9                                      ______________________________________                                    

EXAMPLE 5

The procedure was as described in Example B 2, whereby the processparameters and results are collected in the following Table 5.

                  TABLE 5                                                         ______________________________________                                        Synthesis Gas, H.sub.2 :CO                                                                           1.65    1.65                                           Space Velocity         125     125                                            Volume/Volume · h                                                    Reaction Temperature, °C.                                                                     400     425                                            Reaction Pressure, bar 100     100                                            Total Conversion of    29.6    40.1                                           Synthesis Gas, %                                                              Conversion of CO to    23.3    31.5                                           Hydrocarbons, %                                                               Distribution of Hydrocarbons in Wt. %                                         Methane                21.0    35.0                                           Ethane                 69.9    55.0                                           Propane                5.0     6.1                                            Butane and Higher      4.1     3.9                                            ______________________________________                                    

EXAMPLE 6

The reaction was as in Example B 1.

                  TABLE 6                                                         ______________________________________                                        Reaction of Synthesis Gas On Aluminum Silicate                                According To Example A 6 Which Was Shaped                                     According to Example 7                                                        ______________________________________                                        Temperature °C.  400                                                   Pressure Bar            80                                                    Space Velocity          500                                                   Volume/Volume · h                                                    H.sub.2 /CO in          2.2                                                   Conversion of CO to     17.4                                                  Hydrocarbons                                                                  Total Conversion of     18.0                                                  Synthesis Gas                                                                 Distribution of Hydrocarbons Wt. %                                            Methane                 29.0                                                  Ethane                  62.0                                                  Propane                 5.0                                                   C.sub.4.sup.+           4.0                                                   ______________________________________                                    

EXAMPLE 7

50 grams of commercial Zeolite Y was exchanged analogous to Example A 2and used for synthesis gas conversion.

                  TABLE 7                                                         ______________________________________                                        Temperature °C.  500                                                   Pressure bar            80                                                    Space Velocity          500                                                   Volume/Volume · h                                                    H.sub.2 /CO in          2.2                                                   Conversion of CO to     21.0                                                  Hydrocarbons                                                                  Total Conversion of     24.7                                                  Synthesis Gas                                                                 Distribution of Hydrocarbons Wt. %                                            Methane                 51                                                    Ethane                  41                                                    Propane                 6                                                     C.sub.4.sup.+           2                                                     ______________________________________                                    

EXAMPLE 8

50 grams of the commercial zeolite mordenite in the hydrogen form wasimpregnated according to Example A 6 using 9 grams of zinc acetate andused for the synthesis gas reaction. The results are set forth in Table8.

                  TABLE 8                                                         ______________________________________                                        7% ZnO/Mordenite                                                              Pressure 100 bar H.sub.2 /CO in = 1.72                                                               After 20 h                                             ______________________________________                                        Temperature °C.                                                                         350     375     400   425                                    Space Velocity   650     650     650   650                                    Contraction, %   ˜2                                                                              4.5     7.5   10.3                                   Conversion of CO to                                                                            ˜3                                                                              7.5     11.2  14.2                                   Hydrocarbons, %                                                               Conversion CO + H.sub.2, %                                                                     ˜3                                                                              8.0     13.4  18.5                                   Out H.sub.2 /CO  ˜1.8                                                                            1.85    1.0   1.05                                   Out CO.sub.2, Vol. %                                                                           1.0     1.8     3.5   4.7                                    Distribution of Hydrocarbons                                                  C.sub.1, Wt. %   36.0    37.5    34.6  36.6                                   C.sub.2          39.1    45.7    53.5  56.2                                   C.sub.3          17.8    12.1    8.6   5.9                                    C.sub.4          7.0     3.6     2.4   0.9                                    C.sub.5 +        0.2     1.1     0.9   0.3                                    ______________________________________                                    

The entire disclosure of German priority application P No. 3228270.2 ishereby incorporated by reference.

What is claimed is:
 1. A process for the production of a catalystsuitable for the production of hydrocarbons having high ethaneselectivity consisting essentially of (1) crystalline aluminum silicate,(2) at least one zinc or cadmium compound or a mixture of compounds ofboth zinc and cadmium, and (3) additional silica, said crystallinealuminum silicate being a zeolite having an X-ray diffraction diagram asfollows:

    ______________________________________                                               11.17 ± 0.1                                                                         52                                                                   10.05 ± 0.1                                                                         35                                                                   6.34 ± 0.1                                                                           5                                                                   4.98 ± 0.1                                                                           4                                                                   4.35 ± 0.03                                                                         18                                                                   4.27 ± 0.03                                                                         23                                                                   3.85 ± 0.03                                                                         100                                                                  3.74 ± 0.03                                                                         54                                                                   3.66 ± 0.03                                                                         22                                                                   3.45 ± 0.03                                                                          7                                                                   3.34 ± 0.02                                                                          8                                                                   2.98 ± 0.02                                                                         12                                                                   2.49 ± 0.02                                                                         12                                                                   2.00 ± 0.02                                                                          8                                                            ______________________________________                                    

which comprises reacting a mixture of water, sodium aluminate, sodiumhydroxide, precipitated silica, and ##STR4## at a temperature of 50° to200° C. under autogenous pressure in a closed container, treating thezeolite thus produced with a compound of zinc or cadmium and shapingwith an SiO₂ containing binder.
 2. A process according to claim 1including the step of at least partially converting the zeolite producedto the hydrogen form.